<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<meta name="viewport" content="width=device-width, initial-scale=1.0">
	<title>Document</title>
	<style>
		input:focus {
			background-color: yellow;
		}
	</style>
</head>
<body>
	<form action="url" method="get" name="focus-test">
		<input type="text" name="name" id="name">
	</form>
</body>
</html>